For many years limestone-based rock dust has been the mine rock dust of choice for explosion abatement. Typically limestone mine rock dusts are readily available throughout North America and prevent the propagation of an explosion when applied in a proper manner to all mine surfaces and used in the correct proportion to the coal dust generated during the mining process.
However, in 2011, the National Institute of Occupation Safety and Health (NIOSH) reported that examinations of rock dust samples tended to cake when wetted and subsequently dried. The report revealed that the examined samples formed cakes and were not easily dispersed with the subjective requirement of a “light blast of air.” The rock dust samples NIOSH analyzed contained very fine (e.g., less than 10 microns) particles. Fine particles enhance the caking potential of rock dust when wetted.
Therefore, it may be desirable to provide an economically-viable modified limestone-based rock dust that will be capable of passing the caking evaluation tests established by NIOSH and government regulations, and effectively inerting coal dust.